Cold Climate Air Source Heat Pumps

TimeBandit

Good day, all. I am looking for anyone with real-life experience with Cold Climate Air Source Heat Pumps. The colder the climate, the better. In particular, looking for specific models and how well they perform at sub-freezing temperatures... but any kind of feedback/info/opinions would be appreciated. Thanks in advance!

Techman

heat pump

The colder the climate ,the better. I don't buy it!  I'm not familiar with the Cold Climate brand ,I am familiar with darn near every brand/type/style of HP . I will check it out, tks!

TimeBandit

Not a brand name

Cold climate is not a brand name... I was referring to heat pumps specifically designed to operate in cold climates. )

Jack

Not sure where the Unitary manuf

are on this. Fujitsu, Mitsubishi and Daikin are all making heat pumps that will operate down to -15F. The thing about this is that you have to check each manuf model and it specs for that unit at the desired temperatures.

Matt_67

Mitsubishi hyper heat

We've used the Mitsubishi hyper heat units here in the upper peninsula of michigan. We put them on a stand and use the base pan heater. We used one in a cabin which was intended for use in March through November and it worked well down into the teens. He tried to use it when it was single digits below 0 and it only got the cabin into the 50's. It all depends on heat loss of the structure of course. We just put in our first trane variable speed condensing unit - works great so far but no experience with real cold weather yet.

Techman

heat pump

Not so fast there,cupcake. The "new regular" cold climate heat pump(with inverter technology compressors) has been around for so long now , you threw me for a loop there. They usually require a "wind shield baffel " to work in the lower temps if ACing. BUT there has been a "NEWER" type of HP around for around 15-20 years or so. David Shaw(retired from Carrier ) developed a HP that incorporates two compressors ,Shaw Engineering Associates started developing the unit ,then went out of business and then Nyle Special Products of Bangor , Maine got involved, then Mr. Shaw then with Hallowell International (also of Bangor) got re-involved and then THERE IS/WAS a brand name called ( of all things) "COLD CLIMATE HEAT PUMP". Thanks Mr. intheknow. There is more involved with this story.

Spence

HPs in Cold Weather

Plot your structure heat loss on a balance point chart. Choose a HP of your liking and check the rated caps at 47 and 17 degrees and plot that output. This will immediately show you how much heat you will get with and without back up. Always choose a high HSPF; a 9.5 will produce 2.82 times the amount it uses in energy (HSPF x .297).

Spence

HPs

Cupcake?

Techman

cchp

Said with a lol!!!!!

Spence

LoL

I'm still laughing!



FYI: my design temperature is 14. The worst day last winter was 12 with a 25 MPH wind, gusting to 30+. At 8:00 pm my HP was maintaining 69 degrees inside, and the house faces West, right into the wind. By the way, I don't have back up heat of any kind.

Furnacelady

1st question

Where you live, is electric cheaper than gas. If not stick with gas.

Spence

Electric vs. Gas

Your post is accurate under two conditions. (1) you are below the thermal balance point, and; (2) you are at or below the economic balance point.

TimeBandit

thanks!

I have learned a few things already here... thanks for everyone's feedback. Anyone else in cold areas using air source heat pumps?

Spence

Heat Pumps

Even a reasonably efficient HP will be 1.7:1 at -17 degrees. At that frigid ambient, you will still get 1.7 cents of heat for every penny you put in. Electric heat has a COP of 1. HPs will always be more than 1 because they do not create heat; they transfer it. Moving is always cheaper than making! Heat pumps don't work properly ONLY when they are not properly sized, the duct system is not right (that .10 crap), the terminal units are wrong, and a balance point chart was not used.

meplumber

Psychometric Chart

Being an HVAC guy in Maine, I feel qualified to talk about cold climate heat pump operation.



One thing that is often forgotten when looking at cold climate heat pumps is the physics of the change of state of the refrigerant.  If we use the psychometric chart, we can see that at around 6.63 Btu/lb of enthalpy and with the fan moving 400 cfm per ton, we hit the point where the refrigerant can no longer change state from liquid to gas or vice versa.  The condenser unit (which becomes the evaporator in heat pump mode) has a fan that is sized to operate at ~400 cfm per ton as does the indoor unit.



So.....as the temperature and humidity of the outside air fall, the enthalpy, or the amount of heat contained in one pound of air, also falls.  The performance of the heat pump really has very little to do with the Outdoor Dry Bulb temperature and everything to do with the OSA enthalpy.



For instance, if you had a day where the OSA Dry Bulb was at -10 F and the dew point was at -11 F, there would still be enough enthalpy to theoretically allow the refrigerant to change state.  However if you encountered a day where the OSA Dry Bulb was -3 F but the dew point was at -15F then you would have an OSA Enthalpy below the 6.63 Btu/lb threshold and would not be able to sustain theoretical change of state.



Manufacturers are working around this in several ways.  Most of the Japanese HP manufacturers are using Condenser Fan motors that are capable of more than 400 CFM per ton in heating mode.  Others use a modified hot gas bypass.  Then there is that wonderful Acadia Heat Pump by the now defunct Hallowell.  They were doing some really exotic things with hot gas bypass.  So exotic that it was killing the compressors.  Bristol found out and went nuts.  Hallowell is now bankrupt and their machines are failing all over the place.



Simple answer is that you can't fool physics.  It wins every time.  The winners in the cold climate heat pump race are finding solid work arounds.



Good Luck.